Add seed values support for Query Builder order_by

(feature request #1987)
diff --git a/system/database/drivers/oci8/oci8_driver.php b/system/database/drivers/oci8/oci8_driver.php
index eb01dd1..62f9191 100644
--- a/system/database/drivers/oci8/oci8_driver.php
+++ b/system/database/drivers/oci8/oci8_driver.php
@@ -102,9 +102,9 @@
 	/**
 	 * ORDER BY random keyword
 	 *
-	 * @var	string
+	 * @var	array
 	 */
-	protected $_random_keyword = ' ASC'; // not currently supported
+	protected $_random_keyword = array('ASC', 'ASC'); // not currently supported
 
 	/**
 	 * COUNT string